1. Field of the Invention
This invention relates to cable or reeled tubing-deployed pumping systems for use in oil and gas wells, and more particularly, to an emergency hydraulic release for the locking module discharge head in a cable-deployed or reeled tubing-deployed pumping system. A further embodiment of the invention relates to cable or reeled tubing hydraulic release apparatus for loosening a stuck downhole tool from a well casing for subsequent retrieval, or moving a downhole tool longitudinally to perform an operation in the well.
2. Description of the Background
Artificial lift systems for use in oil and gas wells are well known. One type of artificial lift system is a cable deployed pumping system as previously disclosed, for example, in U.S. Pat. No. 4,913,239. The cable-deployed pumping system allows electric submersible pumps to be installed and retrieved by means of a crush-resistant electrical cable that can be field-spliced and is designed to withstand the gripping forces of an injector and the rigors of downhole service. This is a cost-effective alternative to conventional tubing deployment and offers faster installation and retrieval with smaller equipment and few personnel.
In a standard installation for a cable-deployed pumping system, whether using a conventional pump or inverted pump, an electric submersible pump, motor and locking module discharge head are first connected to the electrical cable using a cable anchor assembly and an electrical penetrator assembly. The pumping system is then injected into the well through production tubing by means such as a modified reeled tubing injector. As the cable is lowered into the well, a collet latch on the locking module engages a locking module landing nipple disposed in the tubing string. After a subsurface safety valve below the landing nipple is opened by control fluid pressure exerted through a control line, the electric submersible pump can be activated to begin pumping well fluids to the surface. When it is desired to retrieve the pumping system from the well, the locking module is disengaged from the landing nipple by pulling upward on the electric cable.
In using the previously known cable-deployed pumping systems, problems have sometimes been encountered when sand bridges or other trash accumulates around the locking module, making it difficult or impossible to disengage and retrieve the system by pulling on the cable from the surface. The pulling force required to break the sand bridge may exceed the tensile strength of the CAPS cable, causing it to fail. A system is therefore needed that will facilitate the disengagement and separation of the locking module from the landing nipple to permit recovery of the locking module and the electric submersible pump.
Another similar problem which is sometimes encountered, is when sand bridges or other trash accumulates around, for example, a well tool such as a packer, packer seal unit, choke, plug or valve, which prevents normal retrieval of the tool. This may occur, for example, when a slickline or wireline unit would ordinarily be employed to retrieve the tool, but is unable to generate sufficient force to pull the tool loose, due to the trash that has accumulated around the tool. In such a situation, an expensive and time consuming fishing job may be required, which may require the use of a rig and running a string of pipe to depth to retrieve the stuck tool.